Electronic structure and surface properties of PrMnO₃ (001): A density functional theory study

In this paper, the surface properties of the (001) surface in PrMnO₃ are investigated using the projector augmented plane wave (PAW) methods within the spin-polarization generalized gradient approximation (GGA+U), where U is on-site Coulomb interaction correction. The result of the total density of states shows a half-metallic ground state for PrMnO₃ in GGA+U treatment. The optimized structure parameters of both cubic and orthorhombic bulk phases are obtained. The electronic properties of the cubic PrMnO₃ (001) surface with PrO- and MnO₂-terminations are discussed. Based on the results of the calculated surface energies, we predict the surface energies of three low-index surfaces follows the sequence of (001)<(111)<(110). The rumpling for the PrO-terminated surface is much larger than that of the MnO₂-terminated surface. Both the PrO- and MnO₂-terminated surfaces display a reduction of d₁₂ interlayer distance and an expansion of d₂₃. Bader effective charge of the ion is much smaller than its formal charge which is due to the partial Mn-O bond covalency. The oxygen-vacancy formation energy in bulk PrMnO₃ is found to be smaller than other perovskites, e.g. LaMnO₃ and SrTiO₃. We find that the formation energy of oxygen-vacancy on MnO₂-terminated surface is lower than the formation energy of oxygen-vacancy on PrO-terminated surface and Sr-doped PrMnO₃ makes oxygen-vacancy formation more easily compared pure PrMnO₃.